The assembly of lipid droplets and their roles in challenged cells

Reese, Michael L.; Goodman, Joel M.

doi:10.15252/embj.2019101816

Cited by 67 publications

(87 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Among the organelles that engage in non-vesicular transport are lipid droplets (LDs) (Henne et al, 2018;Schuldiner and Bohnert, 2017). LDs function at the center of cell metabolism in many ways.…”

Section: Introductionmentioning

confidence: 99%

“…LDs reside in close proximity to both mitochondria and peroxisomes (Henne et al, 2018;Schuldiner and Bohnert, 2017). Contact sites between LDs and mitochondria and between LDs and peroxisomes are thought to facilitate direct channeling of FAs across these organelles' boundaries and to prevent toxicity from free cytosolic FAs (Nguyen et al, 2017;Unger et al, 2010).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

Chang

Weigel

Ioannou

et al. 2019

Preprint

View full text Add to dashboard Cite

Lipid droplets (LDs) are neutral lipid storage organelles that transfer lipids to various organelles including peroxisomes. Here, we show that the hereditary spastic paraplegia protein M1 Spastin, a membrane-bound AAA ATPase found on LDs, coordinates fatty acid (FA) trafficking from LDs to peroxisomes through two inter-related mechanisms. First, M1 Spastin forms a tethering complex with peroxisomal ABCD1 to promote LD-peroxisome contact formation. Second, M1 Spastin recruits the membrane-shaping ESCRT-III proteins IST1 and CHMP1B to LDs via its MIT domain to facilitate LD-to-peroxisome FA trafficking, possibly through IST1 and CHMP1B modifying LD membrane morphology. Furthermore, M1 Spastin, IST1 and CHMP1B are all required to relieve LDs of lipid peroxidation. M1 Spastin's dual roles in tethering LDs to peroxisomes and in recruiting ESCRT-III components to LD-peroxisome contact sites for FA trafficking may help explain the pathogenesis of diseases associated with defective FA metabolism in LDs and peroxisomes.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

Chang

Weigel

Ioannou

et al. 2019

Preprint

View full text Add to dashboard Cite

show abstract

“…Nearly all organisms have the capacity to buffer fluctuations in the availability of energy by storing highly reduced carbons in the form of fats, such as triacylglycerol (TG) in lipid droplets (LDs) (Henne et al, 2018;Onal et al, 2017;Walther et al, 2017). Although LDs can be formed in most cells, the structural mechanisms for the biogenesis of this organelle remain largely unknown.…”

Section: Introductionmentioning

confidence: 99%

Cryo-electron microscopy structure of the lipid droplet-formation protein seipin

Sui

Arlt

Brook

et al. 2018

Preprint

View full text Add to dashboard Cite

Sui et al. report the cryo-EM structure of the conserved luminal domain of the lipid droplet (LD)-formation protein seipin. The structure reveals key features of this domain and suggest a new model for seipin's role in LD formation. SUMMARYMetabolic energy is stored in cells primarily as triacylglycerols in lipid droplets (LDs), and LD dysregulation leads to metabolic diseases. The formation of monolayer-bound LDs from the endoplasmic reticulum (ER) bilayer is poorly understood, but the ER protein seipin is essential to this process. Here, we report a cryo-electron microscopy structure and functional characterization of D. melanogaster seipin. The structure reveals a ringshaped dodecamer, with the luminal domain of each monomer resolved at ~4.0 Å. Each luminal domain monomer exhibits two distinctive features: a hydrophobic helix positioned towards the ER bilayer, and a b-sandwich domain that has structural similarity with lipidbinding proteins. This structure, and our functional testing in cells, suggest a model in which seipin oligomers initially detect forming LDs in the ER via hydrophobic helices and subsequently act as membrane anchors to enable lipid transfer and LD growth. Wolinski et al., 2015). Previous studies of seipin led to different models for its molecular function, including acting as a regulator of the ER Ca 2+ pump SERCA, a molecular scaffold and regulator of lipid metabolism enzymes, and a structural protein facilitating LD growth at ER-LD contact sites (Bi et al., 2014;Pagac et al., 2016;Sim et al., 2012;Talukder et al., 2015;Wang et al., 2016). However, despite considerable efforts, the molecular function of seipin in LD biogenesis remains unclear.As a step toward unraveling seipin's function, we sought to elucidate its molecular structure. Utilizing cryo-electron microscopy, we report here a structural model of Drosophila melanogaster seipin, solved for the luminal domain at ~4.0 Å resolution. This structure reveals seipin to form a dodecamer that positions multiple hydrophobic helices near the ER bilayer and a b-sandwich folded domain with similarity to lipid-binding proteins. We use several approaches to validate this structure, and we test several of its key features in vitro and in cells. Our results suggest a functional model for how seipin functions to detect forming LDs and promote their growth. RESULTS Determination of a cryo-electron microscopy map of Drosophila melanogaster seipinWe purified recombinant D. melanogaster seipin in detergents, and gel-filtration chromatography revealed it to be an oligomer (Fig. S1, A and B), similar to what was reported in other species (Binns et al., 2010;Sim et al., 2014). Consistently, negativestain electron microscopy (EM) analyses showed that seipin particles were monodisperse, and two-dimensional (2D) averages demonstrated distinct views with round or multi-layer barrel shapes (Fig. S1 C).We next analyzed purified seipin by cryo-electron microscopy (cryo-EM). The 2D averages of cryo-EM particle images (Fig. 1, B and C) appeared similar to those ...

show abstract

“…TG synthesis depends on the acyl-CoA:diacylglycerol acyltransferases 1 and/or 2 (DGAT1,2) 10 , which catalyze the covalent addition of a fatty acyl chain to diacylglycerol (DG) 10 . LDs are the core energy storage organelles of adipocytes, but develop in other cell types as well, where they can again act as energy stores for fueling cell intrinsic ATP production via mitochondrial FAO 2,11 .…”

mentioning

confidence: 99%

Triacylglycerol synthesis enhances macrophage inflammatory function

Castoldi

Monteiro

Bakker

et al. 2020

Preprint

View full text Add to dashboard Cite

Macrophages are integral to most tissues. Foam cells, macrophages with lipid droplets (LDs) which are stores of triacylglycerols (TGs) and cholesterol esters (CEs), are found in various disease states 1 . LDs can act as energy stores since TG lipolysis releases fatty acids (FAs) for mitochondrial oxidation (FAO), a process that relies on long-chain FA conversion into acylcarnitines by the enzyme Cpt1a 2 . However, in macrophages, proinflammatory signals result in diminished FAO and increased TG synthesis with LD development 3,4 . We explored the significance of LDs in cells that do not utilize FAO. We show that macrophages stimulated with lipopolysaccharide (LPS) plus interferon-g (IFNg) accumulate TGs in LDs, and long-chain acylcarnitines. In these cells, inhibition of TG synthesis results in diminished LD development, and increased long chain acylcarnitine levels, suggesting that FA fate is balanced between TG and acylcarnitine synthesis. Nevertheless, TG-synthesis is required for inflammatory macrophage function, since its inhibition negatively affects production of proinflammatory IL-1b, IL-6 and PGE2, and phagocytic capacity, and protects against LPS-induced shock in vivo. Failure to make PGE2 is critical for this phenotype, since exogenous PGE2 reverses the anti-inflammatory effects of TG-synthesis inhibition. These findings place LDs in a position of central functional importance in inflammatory macrophages. EJP and ELP are Founders of Rheos Medicines MethodsMice and in vivo experiments C57BL/6 mice (RRID: IMSR_JAX:000664) were from The Jackson Laboratory, and were maintained in specific pathogen-free conditions under protocols approved by the animal care committee of the Regierungspräsidium Freiburg, Germany, in compliance with all relevant ethical regulations. Animals were 6-8 weeks old when used. They were euthanized by carbon dioxide asphyxiation followed by cervical

show abstract

The assembly of lipid droplets and their roles in challenged cells

Cited by 67 publications

References 1 publication

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

Spastin tethers lipid droplets to peroxisomes and directs fatty acid trafficking through ESCRT-III

Cryo-electron microscopy structure of the lipid droplet-formation protein seipin

Triacylglycerol synthesis enhances macrophage inflammatory function

Contact Info

Product

Resources

About